Stabilized degreasing solvent



United States Patent Office 3,049,571 Patented Aug. 14, ,1 962 3,04%571 STABILIZED DEGREAEJNG SOLVENT Winston E. Brown, Lake Jackson, Tern, assignor to The Dow Chemical Company, Midland, Nficln, a corporation of Delaware N Drawing. Filed Mar. 18, 1960, Ser. No. 15,321 19 Claims. (til. 260-6525) This invention relates to a solvent comprising methyl chloroform containing a mixture of inhibitors effective to prevent decomposition of the methyl chloroform when the vapors thereof are in contact with metallic zinc surfaces and to prevent corrosion of the zinc and zinc alloys.

It is Well known that the common chlorinated hydrocarbons which are employed in the degreasing of metals, dry cleaning, and other purposes are subject to decon1p0- sition upon contact with metal surfaces and cause corrosion of such surfaces. It has been long customary to add stabilizing amounts of inhibitors to such solvents to stabilize them against metal induced decomposition and to suppress or prevent corrosive attack upon metal surfaces with which they come in contact. A great multiplicity of agents have been proposed as corrosion inhibitors for such chlorinated solvents but it is generally recognized that the effectiveness of a particular inhibitor or a particular chlorinated solvent cannot be predicted. This is especially true of methyl chloroform as special problems exist with this solvent that do not exist with other chlorinated solvents and it is known that inhibitors which are very effective in stabilizing other chlorohydrocarbons are not effective as stabilizers for methyl chloroform.

Methyl chloroform is recognized as an excellent solvent and there has been a continuing need to render it inert to the presence of metals under the conditions of vapor degreasing. Stabilizers are known which are effective in stabilizing methyl chloroform against decomposition induced by contact with iron and aluminum even at elevated temperatures. It is now known, however, that while pure uninhibited methyl chloroform at elevated temperatures is relatively inert to the presence of zinc, methyl chloroform which is stabilized against decomposition due to contact with other metals, particularly iron and aluminum, tends to decompose badly in the presence of zinc and cause substantial corrosive attack on the Zinc metal. Decomposition of the solvent and corrosion of the zinc occur only when the zinc is exposed to the hot vapors of methyl chloroform stabilized against iron and aluminum induced decomposition. Zinc below the surface of the boiling solvent will remain virtually unaffected. This is due to the fact that these inhibitors, which stabilize methyl chloroform against iron and aluminum, catalyze the attack of methyl chloroform on zinc in the boiling vapors of the solvent. This undesirable property causes a restriction of the utility of methyl chloroform particularly as a solvent in the vapor degreasing field as galvanized equipment is common and many of the articles to be dcgreased are zinc, zinc alloy, such as brass or galvanized iron.

An additional need for a stabilizer system to render the hot vapors of methyl chloroform inert to zinc surfaces is found in the recovery of used solvent. Methyl chloroform may be used in the cold degreasing of metals until it becomes saturated with dirt, grease and other impurities from the metal being cleaned. Spent solvent without the stabilizer system hereinafter proposed cannot be recovered by distillation in the zinc-lined stills commonly used in the industry without damage to the lining thereof.

It is therefore an object of this invention to provide a solvent which is substantially stable in the presence of zinc and non-corrosive to zinc and its alloys as well as other metals. It is a further object of this invention to provide a solvent which is substantially stable to Zinc and its alloys in the presence of other stabilizer systems. It

is a still further object of the present invention to provide a stabilized methyl chloroform solvent which will not in the vapor phase attack zinc. Other and related objects may appear from the following description of the invention and the claims thereto.

It has now been discovered that the corrosive action of methyl chloroform on zinc when the methyl chloroform is stabilized against decomposition by other metals and the accompanying decomposition of methyl chloroform in the presence of zinc may be prevented by the addition thereto of a vicinal epoxide.

Methyl chloroform where used as a vapor degreasing solvent contains minor amounts of certain additives or stabilizers to prevent decomposition of the solvent induced by its contact with metals such as aluminum and iron. Inhibitors such as 1,4-di0xane alone or in combination with nitromethane, secondary butyl alcohol, or monohydric acetylenic alcohols are commonly employed. Such stabilizers are quite effective in rendering the solvent inert to attack of the metal by the degradation products, but greatly increase the ability of zinc, in the boiling solvent vapors, to cause degradation of the solvent and concomitantly increased attack of the metal. This undesirable property of the solvent may be eliminated, however, by the addition thereto of a vicinal inonoepoxide in the amount of from about 0.01 to 5.0 percent by Weight of the solvent mixture. It is preferred to employ the epoxide in the amount of from about 0.10 to 1.5 percent by Weight, however. If an amount less than 0.01 percent is employed no effective stabilization is achieved. Amounts greater than 5 percent may be employed but no advantage is achieved thereby.

In order to achieve the objects of this invention and to produce a suitable solvent for vapor degreasing of metal it is necessary that the methyl chloroform be inhibited against decomposition induced by contact with metals such as iron and aluminum. If it is not thus stabilized the presence of an aliphatic vicinal epoxide will not prevent the degradation of the solvent. Inhibitors for use against iron and aluminum degradation are shown in patents such as US. 2,811,252 and US. 2,838,458. The preferred concentrations of these inhibitors are from 0.5 to 10 percent of 1,4-dioxane and from 0.01 to 3.0 percent nitromethane, secondary butyl alcohol, or monohydric acetylenic alcohol.

Vicinal epoxides as used herein refers to aliphatic epoxides containing an ethylene oxide group. While many vicinal monoepoxides are operable to some extent it is desirable to employ vicinal monoepoxides containing from 4 to 6 carbon atoms, for example, 1,2-butylene oxide, isobutylene oxide, cis-2,3- and trans-2,3-butylene oxide, 3,4- epoxybutene transand cis-2,3-pentene oxide, Z-methyl- 2,3-epoxybutane, 1,2-epoxycyclopentene and 2,3-dimethyl2,3epoxybutane.

The following examples illustrate the present invention but are not to be construed as limiting:

Example 1 To demonstrate the relative stability of uninhibited methyl chloroform to zinc a test run was made as follows:

A flask was partly filled with uninhibited methyl chloformed due to decomposition of the solvent and ZnCl formed by corrosive action of the solvent on the zinc.

Example 2 In the same equipment, and under the same conditions employed in Example 1, a sample (1) of methyl chloroform containing 4 percent by Weight of 1,4-dioxane, a sample (2) of methyl chloroform containing 4 percent by weight of 1,4-dioxane and 0.05 percent by weight of secondary butyl alcohol and a sample (3) of methyl chloroform containing 4 percent by weight of 1,4-dioxane and 0.5 percent by weight of nitromethane were boiled for seven days. The test strips in every case were found to be badly corroded. The methyl chloroform, sample (1) was found to contain 110 p.p.m. chloride, sample (2) Was found to contain 150 p.p.m. chloride, and sample (3) was found to contain p.p.m. chloride. However, the zinc strips in sample (3) were corroded more severely than in the other two test strips.

Example 3 In the same equipment and under the same conditions employed in Example 1, samples of methyl chloroform were tested employing vicinal monoepoxides in combination With various stabilizers as shown in the following table:

As a result of exposure of zinc for seven days to the solvent action the total chloride content of each combination above listed was less than 0.50 p.p.m. In all cases the zinc strips were bright and unaffected at the end of the exposure.

I claim:

1. A composition of matter comprising methyl chloroform containing a minor amount of 1,4-dioxane and having dissolved therein a stabilizing amount of a vicinal monoepoxide having from 4 to 6 carbon atoms.

2. A composition of matter comprising methyl chloroform containing a minor amount of 1,4-dioxane and a minor amount of a compound selected from the group consisting of nitromethane, secondary butyl alcohol and a lower monohydric acetylenic alcohol and having dissolved therein a stabilizing amount of a vicinal aliphatic monoepoxide having from 4 to 6 carbon atoms.

3. A composition of matter comprising methyl chloroform containing a minor amount of nitromethane and dissolved therein a stabilizing amount of a vicinal monoepoxide having from 4 to 6 carbon atoms.

4. A composition of matter comprising methyl chloroform containing a minor amount of secondary butyl alcohol and having dissolved therein a stabilizing amount of a vicinal monoepoxide having from 4 to 6 carbon atoms.

5. A vapor degreasing solvent composition comprising methyl chloroform containing a small stabilizing amount of 1,4-dioxane and having dissolved therein from 0.05 to 5 percent by Weight of a vicinal monoepoxide having from 4 to 6 carbon atoms.

6. A vapor degreasing solvent composition comprising methyl chloroform containing stabilizing amounts of 1,4- dioxane and nitromethane and having dissolved therein from 0.05 to 5 percent by weight of a vicinal monoepoxide having from 4 to 6 carbon atoms.

7. A vapor degreasing solvent composition comprising methyl chloroform containing stabilizing amounts of 1,4- dioxane and secondary butyl alcohol having dissolved therein from 0.05 to 5 percent by weight of a vicinal monoepoxide having from 4 to 6 carbon atoms.

8. A vapor degreasing solvent composition comprising methyl chloroform containing stabilizing amounts of 1,4- dioxane and a monohydric acetylene alcohol having dissolved therein from 0.05 to 5 percent by weight of a vicinal monoepoxide having from 4 to 6 carbon atoms.

9. A composition of matter comprising methyl chloroform containing a stabilizing amount of 1,4-dioxane and from 0.10 to 1.5 percent by weight butylene oxide.

10. A composition of matter comprising methyl chlorofor-m containing a stabilizing amount of 1,4-dioxane and from 0.10 to 1.5 weight percent of amylene oxide.

11. A composition of matter comprising methyl chloroform containing a stabilizing amount of 1,4-dioxane and from 0.10 to 1.5 weight percent of hexylene oxide.

12. A composition of matter comprising methyl chloroform containing a stabilizing amount of nitrornethane and from 0.10 to 1.5 weight percent of butylene oxide.

13. A composition of matter comprising methyl chloroform containing a stabilizing amount of nitromethane and from 0.10 to 1.5 weight percent of amylene oxide.

14. A composition of matter comprising methyl chloroform containing a stabilizing amount of secondary butyl alcohol and from 0.10 to 1.5 weight percent of butylene oxide.

15. A composition of matter comprising methyl chloroform containing a stabilizing amount of a secondary butyl alcohol and from 0.10 to 1.5 weight percent of amylene oxide.

16. A composition of matter comprising methyl chloroform containing a stabilizing amount of secondary butyl alcohol and from 0.10 to 1.5 weight percent of hexylene oxide. 1

17. In a process for stabilizing methyl chloroform containing 1,4-dioxa ne against decomposition in the presence of zinc, the improvement which comprises adding from 0.05 to 5 weight percent of butylene oxide thereto.

18. In a process for stabilizing methyl chloroform containing 1,4-dioxane against decomposition in the presence of zinc, the improvement which comprises adding from 0.05 to 5 weight percent of amylene oxide thereto.

19. In a process for stabilizing methyl chloroform containing 1,4-dioxane against decomposition in the presence of zinc, the improvement which comprises adding from 0.05 to 5 weight percent of hexylene oxide thereto,

References Cited in the file of this patent UNITED STATES PATENTS 2,371,645 Aitchison et al Mar. 20, 1945 2,811,252 Bachtel Oct. 20, 1957 2,838,458 Bachtel June 10, 1958 2,923,747 Rapp Feb. 3, 1960 FOREIGN PATENTS 773,187 Great Britain Apr. 24, 1957 

1. A COMPOSITION OF MATTER COMPRISING METHYL CHLOROFORM CONTAINING A MINOR AMOUNT OF 1,4-DIOXANE AND HAVING DISSOLVED THEREIN A STABILIZING AMOUNT OF A VICINAL MONOEPOXIDE HAVING FROM 4 TO 6 CARBON ATOMS. 